1. Field of the Invention
This invention relates to a living body guidance control method for a biometrics authentication device and to a biometrics authentication device which perform individual authentication by utilize biometrics characteristics, which are characteristics of a portion of the human body, and in particular relates to a living body guidance control method for a biometrics authentication device and to a biometrics authentication device which detect biometrics characteristics by contact-free means to obtain biometrics information.
2. Description of the Related Art
There are numerous portions of the human body which can be used to differentiate the individual, such as fingerprints and toeprints, the retinas of the eyes, facial features, and blood vessels. With advances in biometrics technology in recent years, various devices have come to be offered which recognize biometrics characteristics which are characteristics of such portions of the body to perform individual authentication.
For example, comparatively large amounts of individual characteristic data are obtained from blood vessels in the fingers, palms, and backs of the hands. Moreover, blood vessel (vein) patterns remain unchanged throughout life from infancy and are regarded as being completely unique, and so are well-suited to individual authentication. To take the example of blood vessel images of the palm of a hand, at the time of registration or authentication, the user brings his palm close to an image capture device. The image capture device emits near-infrared rays, which are incident on the palm. The image capture device uses a sensor to receive the near-infrared rays which rebound from the palm.
Hemoglobin in the red corpuscles flowing in the veins has lost oxygen. This hemoglobin (reduced hemoglobin) absorbs near-infrared rays at wavelengths near 760 nanometers. Consequently when near-infrared rays are made incident on the palm of a hand, reflection is reduced only in the areas in which there are veins, and the intensity of the reflected near-infrared rays can be used to identify the positions of veins through contact-free image capture.
The user uses an image capture device to register vein image data of the palm of his own hand in a server or on a card. Then, in order to perform individual authentication, the user employs an image capture device to cause the vein image data of his own hand to be read. The registered vein image retrieved using a user ID or similar is verified against the vein pattern of the vein image for verification thus read, and individual authentication is performed.
In detection of biometrics information by such contact-free means, the body can freely move relative to the image capture device 100, and in particular the hand can be moved freely. On the other hand, the portion of the body for detection must be positioned within the range of image capture of the image capture device in order to enable precise detection.
In the prior art, methods have been proposed in which seals and other means have been used to provide an example of positioning of the hand, the position and inclination of the palm has been detected from captured images, and when precise image capture has not been possible, visible indications and voice output have been used to indicate that the position or inclination of the hand is inappropriate (see for example, WO04/021884 (FIG. 3 and FIG. 15)). In such proposed methods, an image of the entire hand is captured, the image is compared with an average shape of the hand which has been registered, and the position and inclination of the hand are detected.
Further, methods have been proposed in which a judgment is made as to whether the shape of the hand of which an image is captured is appropriate for verification, based on the positions of portions of the palm, such as for example the spreading of the fingers, the position of the wrist, and the position of the entirety of the hand within the image capture range, and in which guidance in positioning the hand is provided to the user (see for example, Japanese Patent Laid-open No. 2006-107401 (Japanese Patent Application 2004-296976)).
In detection of biometrics information by contact-free means, detection is contact-free, and moreover the body, and in particular the hand, fingers and similar can move freely. Hence there are many cases in which the user does not remember the state of image capture of the body part at the time of registration, and so the state of image capture of the body part at the time of authentication is different, and consequently the authentication result is not satisfactory even when the user is the individual in question. If such cases occur frequently, the time required for authentication is increased, and moreover the user, as the individual in question, becomes increasingly distrustful of biometrics authentication.
In methods of the technology of the prior art, in which a common configuration is indicated to the user or a judgment is made as to the appropriateness for verification determined in advance, noise in the biometrics detection device and differences in the detection state at the time of biometrics detection can be eliminated. But because the image capture configuration is not the configuration at the time of registration of the user, there is the concern that the result of verification of registered data against verification data at the time of authentication may not be satisfactory, even if guidance is provided so as to conform to the common configuration.
In other words, there are always individual differences in the image capture configuration. For example, because contact-free detection is used, the size and inclination of the hand of which an image is captured, the spreading of the fingers, and similar may be different at the time of registration and at the time of authentication, and the size of the hand of the individual differs from one person to another (for example, between men and women, and older and younger persons).
Further, because in actuality the human body is detected, changes in physical condition must also be considered; if there are changes in physical condition between the time of registration and the time of authentication, there may be difficulty in authenticating the user at the time of authentication even when the user is the same person, so that problems may arise. For example, in vein authentication, there are numerous causes of changes, such as heartbeat, the timing of image capture, the manner in which the hand is held, and similar.
As a consequence, impediments arise to the spread of biometrics authentication in ubiquitous devices which can be employed by anyone, anywhere, at any time. Moreover, if verification rates are not sufficient, and if problems arise for biological or biometrics reasons, the spread of such technology may be hindered for both users and device manufacturers.